CVE-2026-7309: Red Hat OpenShift Information Disclosure

CVE-2026-7309 Overview

CVE-2026-7309 is an information disclosure vulnerability in the Red Hat OpenShift Container Platform build system. A user holding the edit ClusterRole can inject arbitrary environment variables, including LD_PRELOAD and http_proxy, into docker-build containers through the buildconfigs/instantiate API endpoint. The flaw represents an incomplete fix for a prior vulnerability and impacts the confidentiality of build traffic. The issue is classified under [CWE-426: Untrusted Search Path] and affects OpenShift Container Platform 4.0.

Critical Impact

Authenticated users with edit permissions can intercept or redirect build traffic by manipulating runtime environment variables in build containers.

Affected Products

• Red Hat OpenShift Container Platform 4.0
• Build system components handling docker-build strategy
• buildconfigs/instantiate API endpoint

Discovery Timeline

• 2026-04-28 - CVE-2026-7309 published to NVD
• 2026-05-07 - Last updated in NVD database

Technical Details for CVE-2026-7309

Vulnerability Analysis

The vulnerability resides in the OpenShift build subsystem responsible for executing docker-build strategy builds. A user with the edit ClusterRole has legitimate access to create and trigger BuildConfigs within their namespace. The flaw allows that user to supply arbitrary environment variables through the buildconfigs/instantiate API, which are then passed to the build container at runtime.

Variables such as LD_PRELOAD change the dynamic linker behavior inside the build container, while http_proxy redirects outbound HTTP traffic to an attacker-controlled destination. The result is exposure of build-time network traffic, which may include credentials, source artifacts, or registry tokens transmitted during the build.

This issue is documented as an incomplete remediation of an earlier vulnerability in the same code path. The previous fix did not cover the full set of injectable environment variables reachable through the instantiate API.

Root Cause

The build controller does not sanitize or restrict the environment variable names accepted from the BuildConfig instantiate request. Reserved or security-sensitive variables such as LD_PRELOAD, LD_LIBRARY_PATH, and proxy-related variables are accepted without filtering, allowing them to influence the runtime behavior of the build process and its outbound network traffic.

Attack Vector

An authenticated user with the edit ClusterRole submits a crafted request to the buildconfigs/instantiate API. The request includes environment variable definitions that override proxy settings or alter library loading inside the build container. When the build executes, traffic that would normally reach trusted endpoints, such as source repositories or container registries, is redirected through the attacker-controlled proxy. The attacker observes the contents of that traffic, achieving information disclosure without elevating privileges beyond the edit role.

No public proof-of-concept exploit is available, and the vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog. The EPSS score is 0.026%.

Detection Methods for CVE-2026-7309

Indicators of Compromise

• BuildConfig or Build resources containing environment variables named LD_PRELOAD, LD_LIBRARY_PATH, http_proxy, https_proxy, or no_proxy set by non-administrative users.
• Build pods making outbound network connections to unexpected hosts or non-standard proxy endpoints.
• Audit log entries showing create actions on the buildconfigs/instantiate subresource by users holding only the edit ClusterRole.

Detection Strategies

• Review Kubernetes audit logs for calls to /apis/build.openshift.io/v1/namespaces/*/buildconfigs/*/instantiate and correlate with the requesting user's bound roles.
• Inspect Build and BuildConfig manifests for spec.strategy.dockerStrategy.env entries containing sensitive variable names.
• Compare build container egress traffic patterns against an established baseline of expected registry and source-control destinations.

Monitoring Recommendations

• Forward OpenShift API audit logs and build pod network telemetry to a centralized analytics platform for correlation.
• Alert on any BuildConfig modification that introduces environment variables matching a deny-list of dynamic linker and proxy variables.
• Track build pod DNS queries and TCP connections to detect redirection through unauthorized proxies.

How to Mitigate CVE-2026-7309

Immediate Actions Required

• Apply the security update referenced in the Red Hat CVE-2026-7309 Advisory once available for your OpenShift release stream.
• Audit all users and ServiceAccounts bound to the edit ClusterRole and remove unnecessary grants.
• Review existing BuildConfigs for injected proxy or linker variables and remediate any unauthorized entries.

Patch Information

Red Hat tracks this issue under Red Hat Bug Report #2463451. Consult the Red Hat CVE-2026-7309 Advisory for fixed versions and errata that apply to your OpenShift Container Platform deployment.

Workarounds

• Restrict the edit ClusterRole using an admission controller policy that rejects BuildConfigs containing LD_PRELOAD, LD_LIBRARY_PATH, or proxy-related environment variables.
• Use a custom Role that excludes create and update permissions on buildconfigs/instantiate for untrusted users.
• Enforce egress network policies on build namespaces to prevent build pods from reaching unauthorized proxy endpoints.

# Example OPA/Gatekeeper-style constraint concept to block sensitive env vars in BuildConfigs
# Reject BuildConfig env entries with names matching the deny-list
DENY_VARS="LD_PRELOAD LD_LIBRARY_PATH http_proxy https_proxy no_proxy"
oc get buildconfig -A -o json | \
  jq -r '.items[] | select(.spec.strategy.dockerStrategy.env[]?.name as $n | $n | IN("LD_PRELOAD","LD_LIBRARY_PATH","http_proxy","https_proxy","no_proxy")) | "\(.metadata.namespace)/\(.metadata.name)"'